1. Field of the Invention
The present invention relates to a pattern writing apparatus with a spatial light modulator and a block number determining method for determining the number of modulation blocks of a spatial light modulator used for actual pattern writing in a pattern writing apparatus.
2. Description of the Background Art
Conventionally, a technique for writing a pattern on a photosensitive material by using a spatial light modulator has been suggested. As such a technique, for example, Japanese Patent Application Laid Open Gazette No. 2003-332221 (Document 1) discloses a technique where an irradiation region group onto which a DMD (Digital Micromirror Device) is projected is scanned over a photosensitive material in a scanning direction which is tilted relative to a direction of arrangement of the irradiation region group, whereby writing a pattern on a writing cell group which is set on the photosensitive material at higher density than the irradiation region group. Document 1 also discloses a method of writing at double-speed by controlling ON/OFF of light irradiation of each irradiation region every time the irradiation region group moves a distance equal to two writing cell, and a method for speeding up pattern writing with reduction of time required for input of writing data to the DMD, where a plurality of mirror blocks are arranged in a column direction, each mirror block is composed of a plurality of micromirrors arranged along a row direction, and only a few mirror blocks are used for pattern writing.
When light from a light source such as a discharge lamp or the like is directed on a photosensitive material through an optical system, if it is intended to increase an amount of applied light per unit area on the photosensitive material by reducing the size of a region where the light is emitted, an ideal light amount cannot be obtained due to the technical limitation of convergence of light in the optical system in some cases. Thus, if only a few blocks are used in writing a pattern on the photosensitive material with low sensitivity (i.e., light amount required for exposure is large) in the method of Document 1, a scan speed of the irradiation region group on the photosensitive material has to be set low from the viewpoint of application of necessary light amount on the photosensitive material, and this causes limitation in the speeding up of pattern writing.